I need iOS 13 software

The real problem......you cannot install iOS 13 on an iPhone 6.

The iPhone 6 can only handle up to iOS 12.5.7.....and nothing higher.

If you want to use newer apps, you will need a new phone. If you want to run iOS 16, you will need at least an iPhone 8.

Your iPhone 6, released by Apple over eight years ago, cannot run iOS 13 or later.